Volume 19 Issue 4

The concentrations of Sr, Tl, and V in soils and plant organs were evaluated at a copper mining site. These are heavy metals that are extremely dangerous and harmful to human and environmental health and, therefore, are on the ATSDR substance priority list. Within the scope of the study, soil samples were taken from different soil depths in the spoil area, the rehabilitation area where planting was performed and adult trees that were at least 20 years old, and the forest area. Soil samples were taken from the rehabilitation and forest areas where Pinus nigra Arnold., Pinus sylvestris L., and Robinia pseudoacacia L. species grow, and leaf, bark, wood, and root samples were taken from trees in the same areas. The study evaluated variations in heavy metal concentrations in soils based on species and soil depth and in plants based on plant species and organs. The study found that the heavy metal concentrations in soils and plant organs generally varied depending on plant species, while these variations were insignificant depending on soil depth. The highest concentrations by species were generally obtained for Sr in Robinia pseudoacacia and for Tl and V in Pinus nigra.

The durability of small-diameter larch wood was studied with respect to its treatments with wood tar and wood vinegar in three environments—underground, underwater, and outdoors—for 53 months. This study involved assessing wood cell wall deterioration using optical microscopy, X-ray computed tomography imaging, and X-ray diffraction, along with evaluating various physical and mechanical properties using Korean standards. Severe deterioration was observed in vinegar-treated sapwood after being buried underground. Collapsed cells were often found in untreated and wood vinegar-treated wood buried underground. Noticeable decreases in the physical and mechanical properties were observed in the sapwood of wood vinegar-treated wood buried underground. The wood tar-treated wood buried underground remained relatively intact with minimal changes in its physical properties. No significant degradation was observed in the wood discs submerged in water, and there was no difference in density, shrinkage, hardness, and shear strength between the untreated and preserved wood submerged in water. Under outdoor conditions, wood vinegar-treated wood showed less degradation of the wood discs than untreated and wood tar-treated wood. In conclusion, wood tar enhanced the durability of the wood when it was buried in soil, whereas the wood vinegar treatment provides an advantage when exposed to outdoor conditions.

The present research aimed to increase the accuracy of predicting the maximum force required to compress a solid cardboard box. Changes in the technology of solid cardboard production and the design of packaging help to increase the durability of packaging; however, typical estimation methods do not take these changes into account. By determining the number of important parameters of the box and using a specific approach, it was possible to develop a semiempirical model of the maximum force that compresses the box and simplifies its description. By using this model, the amount of solid board required for a specific package can be reduced without reducing the life of the box. The maximum force prediction method is also suitable for creating other box models at different moisture levels.

This research aimed to determine the impact of the mechanical densifying process of wood material on the varnish surface adhesion strength. Specimens from black pine (Pinus nigra) and Uludag fir (Abies bornmuelleriana Mattf.) were subjected to densification in a hydraulic press at 140 °C to the extent of 25% and 50% in the radial direction. While densification increased the surface adhesion strength of the varnish layer in black pine, the value decreased in fir. Regarding the interaction between densification ratio, surface treatment, and wood type, the highest surface adhesion strength of the varnish layer was found in black pine + unsanded surface + 25% densification, and the lowest was in Uludag fir + unsanded surface + 50% densification. It can be stated that the densification process creates high adhesion values for the polyurethane varnish in the black pine wood type. The sanding process has an intensifying effect on these values, and the products that were obtained from the polyurethane varnished samples do not require sanding. Considering these situations can provide significant advantages in projects with wood materials subjected to the densification process.

Thermal modification is a process capable of improving properties affecting wood performance, such as biological durability. This study aimed to assess the potential of thermal modification in enhancing the resistance of Couratari sp. wood to deterioration by Trametes versicolor, Nasutitermes corniger, and Cryptotermes brevis. Five treatments were analyzed, represented by the untreated and thermally modified wood at 180, 190, 200, and 210 °C. The wood’s chemical composition and resistance to biodeterioration in laboratory tests were evaluated. Thermal modification, especially at 210 °C, altered the chemical composition and increased the wood’s durability class against the fungus. However, the process did not affect termite attack. There was a significant positive correlation between corrected mass loss and hemicellulose and total extractive contents, as well as mass loss caused by T. versicolor and lignin and hemicellulose contents. The use of thermal modification in 190 °C is recommended for Couratari sp. wood due to its enhanced biological durability, with 210 °C being particularly effective.

China has abundant straw resources; however, the utilization of straw waste resource remains challenging. In this work, corn straw fiber and corn straw ash were applied to concrete as raw material after pretreatment. Through mechanical and thermal conductivity tests, it was concluded that the tensile strength of the corn straw fiber was 160.5 MPa after alkali treatment. The corn straw fiber and corn straw powder did not enhance the compressive strength of concrete. Compared with original concrete, the thermal conductivity of concrete added with 1.5% corn straw powder decreased by 25.9%, and the thermal conductivity of concrete with 5% corn straw ash was reduced by only 5.2%. Through thermogravimetric analysis of the concrete, it was found that the internal weakly bound water and strongly bound water will be lost in the range 100 °C to 160 °C, Ca(OH)₂ will decompose from 420 °C to 500 °C, and CaCO₃ will decompose approximately at 800 °C. It is recommended that corn straw powder and corn straw ash can be added at 1.5% and 5% concentrations to ensure that the mechanical properties can meet the engineering requirements and achieve good insulation performance.

In this study, the importance of the materials and designs used in aircraft furniture is considered, and products are recommended for material selection for sustainable aircraft interiors. The type of composite material produced from waste paper, a type of material that has never been used in aircraft before, has potential as a material choice that can be used in the aviation industry in terms of its contribution to recycling, cost, lightness, and water resistance. Conditions such as flammability, durability, compatibility with other materials and lightness of the materials used in aircraft equipment are important, and some alternative material options have been evaluated.

The biodegradation kinetics of paper materials with various chemical additives was studied, focusing on their potential tunability. Paper materials with additives, including retention aid, hydrophobic agent, and wet and dry strength agents, were explored in two forms: disintegrated fiber and paper form. Using the Gompertz equation, biodegradation kinetics were modeled to calculate the lag phase, initial biodegradation rate, and ultimate biodegradation extent. All paper materials showed higher biodegradation extents than microcrystalline cellulose (MCC) due to the highly biodegradable nature of hardwood bleached pulp. Disintegrated paper materials exhibited similar lag phase values and ultimate biodegradation to MCC regardless of treatment, while punched paper materials showed noticeable differences, suggesting that fiber disintegration plays a critical role in initiating biodegradation. Hydrophobic and wet strength treatments, such as alkyl ketone dimer (AKD) and wet-strength agents (PAE), respectively, significantly increased the lag phase, but their ultimate biodegradation extent remained intact. These findings highlight that the biodegradability of paper materials can be preserved even after chemical treatments, underscoring their environmentally friendly potential.

The high extractives content in rice straw severely hinders surface adhesion, resulting in poor strength and dimensional stability of rice straw particleboard bonded with castor oil-based polyurethane (CPUR) resin. In this study, rice straw was pretreated with liquid hot water (LHW) at 150 °C for 20 min to reduce its extractives content for particleboard production with CPUR resin. The effects of LHW pretreatment on the chemical composition of the rice straws was evaluated. In addition, effects of CPUR resin dosage and density on mechanical properties and dimensional stability of the rice straw particleboards were investigated. The results indicated that LHW pretreatment significantly reduced the extractives and hemicellulose contents of the rice straw. The LHW pretreatment significantly improved the mechanical properties and dimensional stability of the rice straw particleboards. The overall performances of the rice straw particleboards were enhanced as the CPUR dosage increased. Increase of density led to upgraded mechanical properties but lowered dimensional stability of the rice straw particleboards.

Development of scrimber composites and other engineered wood products from low-value wood and wood waste provides an effective opportunity to preserve natural resources, minimize waste, and innovate the production of higher-performance, environment-friendly construction materials. In this study, peeler cores, which are the center of poplar logs remaining after the peeling process in the veneer production, were utilized to develop scrimber composites. This study investigated the effects of different resins, including phenol-formaldehyde (PF) and urea formaldehyde (UF), as well as hydrothermal treatments at various temperatures (60 °C and 130 °C), on the physical and mechanical properties of the scrimber composites. Chemical changes in wood components and morphological changes in wood cell walls resulting from hydrothermal treatment were analyzed using Fourier transform infrared spectroscopy and scanning electron microscopy. To clarify how resin type and hydrothermal treatment affect structural performance, several physical and mechanical properties of scrimber composites, including thickness swelling, water absorption, internal bond strength, bending modulus of elasticity, and modulus of rupture, were measured. The test results revealed that hydrothermally treated wood scrims at 130 °C, when bonded with PF resin, produced scrimber composites with superior structural performance.